/*
 * JBoss, Home of Professional Open Source
 * Copyright 2006, Red Hat, Inc. and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.jdiameter.api;

/**
 * Interface for JDiameter classes which provide the ability to retrieve the 
 * delegate instance when the instance in question is in fact a proxy class.
 * The wrapper pattern is employed by many JDiameter stack implementations to
 * provide extensions beyond the traditional JDiameter API that are specific to a
 * data source. Developers may wish to gain access to these resources that are wrapped (
 * the delegates) as proxy class instances representing the the actual resources.
 * This interface describes a standard mechanism to access these wrapped resources
 * represented by their proxy, to permit direct access to the resource delegates.
 * 
 * @author erick.svenson@yahoo.com
 * @author artem.litvinov@gmail.com
 * @version 1.5.1  Final
 */
public interface Wrapper {

  /**
   * Returns true if this either implements the interface argument or is directly or indirectly a wrapper for
   * an object that does. Returns false otherwise. If this implements the interface then return true, else if t
   * his is a wrapper then return the result of recursively calling isWrapperFor on the wrapped object. If
   * this does not implement the interface and is not a wrapper, return false. This method should be implemented
   * as a low-cost operation compared to unwrap so that callers can use this method to avoid expensive unwrap
   * calls that may fail. If this method returns true then calling unwrap with the same argument should succeed.
   * @param iface A Class defining an interface that the result must implement.
   * @return true if this implements the interface or directly or indirectly wraps an object that does.
   * @throws InternalException If no object found that implements the interface
   */
  boolean isWrapperFor(java.lang.Class<?> iface) throws InternalException;

  /**
   * Returns an object that implements the
   * given interface to allow access to non-standard methods, or standard methods
   * not exposed by the proxy. The result may be either the object found to implement
   * the interface or a proxy for that object. If the receiver implements the interface
   * then that is the object. If the receiver is a wrapper and the wrapped object implements
   * the interface then that is the object. Otherwise the object is the result of calling unwrap
   * recursively on the wrapped object. If the receiver is not a wrapper and does not implement the
   * interface, then an SQLException is thrown.
   *
   * @param iface A Class defining an interface that the result must implement.
   * @return an object that implements the interface. May be a proxy for the actual implementing object.
   * @throws InternalException If no object found that implements the interface
   */
  <T> T unwrap(java.lang.Class<T> iface) throws InternalException;

}
